Nb 3d and O 1s core levels and chemical bonding in niobates

A set of available experimental data on binding energies of Nb 3d5/2 and O 1s core levels in niobates has been observed with using energy difference (O 1sNb 3d5/2) as a robust parameter for compound characterization. An empirical relationship between (O 1sNb 3d5/2) values measured with XPS for Nb5+-niobates and mean chemical bond length L(NbO) has been discussed. A range of (O 1sNb 3d5/2) values possible in Nb5+-niobates has been defined. An energy gap ∼1.4-1.8 eV is found between (O 1sNb 3d5/2) values reasonable for Nb5+ and Nb4+ states in niobates.